I can confirm that 'Apple memory' does seem to have a factor in this for some folks.
I too have been plagued by this safe mode hung trouble. I was asked to try some actions in Safe Mode by Apple support for an unrelated issue when I stumbled across this non-booting-into-safe-mode behavior.
In my case I'm running 10.7.5. Tried safe-mode booting multiple times - no luck. Ran diskutility several times - no difference. Rebooted into single-user mode and manually fsck'd the harddrive - still no improvement or progress beyond the 'extended attributes' examination step.
I finally dug out my original memory, removed all my RAM, and installed a single 2G stick of the mem that came with the system - Safe Mode finally booted just fine.